Synthesis of silver decorated magnetic Fe3O4/alginate polymeric surfactant with controllable catalytic activity toward p-NP removal and enzymatic-mimic activity for solid-colorimetric H2O2 detection

In this study, a self-assembly method has been employed for providing a hybrid silver magnetite nanocomposite with superior catalytic and enzymatic peroxidase mimic activity. Interestingly, the tail variation of a newly synthesized polymeric surfactant showed a controlling impact in improving the catalytic activity of the silver-magnetic nanocomposite as a unique study. The hybrid composites were characterized via TEM, SEM, and XRD, revealing the successful preparation of self-assembled AgNPs on the magnetite Fe3O4 nanocomposite surface. The hydrophobic chain of the surfactant improved the catalytic performance of both bare magnetic Fe3O4, and also the silver decorated hybrid magnetic nanocomposite Fe3O4@AMALG8/12@Ag. The decorated Fe3O4@AMALG12@Ag with longest hydrophobic tail exhibited higher catalytic reduction activity to convert p-nitrophenol (p-NP) into p-aminophenol (p-AP) than Fe3O4@AMALG18@Ag which prepared using shorter hydrophobic tail. The engineered hybrid magnetic nanocomposite exhibited super peroxidase mimic activity compared to bare one toward converting the colorless o-phenylenediamine (OPD) into the yellow 2, 3-diaminophenazine (DAP). In the same context, the surfactant participated significantly in improving the peroxidase activity as well. Ultimately, the decorated Fe3O4@AMALG12@Ag was integrated in agarose hydrogel structure with OPD as a peroxidase substrate for colorimetric sensing the H2O2. The solid kit exhibited 0 to 1250 μM as a linear dynamic range with low limit detection (LOD) of 14 μM. The developed solid kit could be applied for detecting different biomarkers such as glucose, lactate, uric and cholesterol based on selective enzymatic release of H₂O₂.